According to the semiconservative model, after one round of replication, every new DNA double helix would be a hybrid that consisted of one strand of old DNA bound to one strand of newly synthesized DNA.
A thorough medical evaluation is necessary to determine the cause of a slow heart rate. An electrocardiogram (EKG or ECG), laboratory tests, and other diagnostic studies may be done. Potential medical causes of a slow heart rate include: abnormal heart rhythms.
Aging or heart disease damages your sinus node's ability to set the correct pace for your heartbeat. Such damage can cause slower than normal heartbeats or long pauses between heartbeats. The damage also can cause your heart to switch between slow and fast rhythms. This condition is called sick sinus syndrome.